This is Essay 3 of the Collection of 'Essays on Cognitive Physical Science' in the repository UPSpace of the University of Pretoria.Essay 3 is the author's first comprehensive description of a model of mind from a physicist's perspective which meets the minimum requirements for such a perspective, inter alia the requirement of a concrete specificity of the underlying physical structure and details. It therefore supersedes the Parallel-Systems Mind Model of Essay 1 (hdl.handle.net/2263/16600), which falls short of this requirement, although many of its features and implications remain valid.Essay 3 is introduced by a discussion of what distinguishes the concept of 'understanding something' for a physicist from that for researchers in other disciplines. This is where the concept of 'levels of logic' (elaborated in Essay 2, hdl.handle.net/2263/43388) plays a decisive role. All further reasoning towards the author's model of mind is based on this physicist's notion of understanding.